1. Field of the Invention
This invention relates to a method for producing an electrochromic device.
2. Prior Art
An electrochromic device is generally produced by sealing the periphery, except for a portion thereof, of a pair of electrically conductive substrates, at least one of which is transparent, placed In a spaced-apart opposing relationship so as to assemble a cell having an injection port formed by the unsealed portion and filling the inner space of the cell by charging through the port an electrolyte or the precursor thereof in a vacuum. The injection port of the cell is then sealed by filling and curing therein a photo-setting or thermosetting acrylic resin or epoxy resin adhesive.
However, such a method for sealing or closing the port requires a step of removing the electrolyte adhered around the injection port prior to filling the adhesive. If the electrolyte is not removed completely, the adhesive can not seal the port sufficiently. Furthermore, the above sealing method fails to obtain satisfactory sealing strength due to an insufficient cure of the adhesive caused by the contact thereof with the electrolyte.
Japanese Laid-Open Patent Publication Nos. 2-114237 and 6-250230 disclose a two-step sealing method to solve the foregoing problems.
Japanese Laid-Open Patent Publication No. 2-114237 discloses a method which comprises a primary sealing and a secondary sealing. In this method, first of all, there is prepared a cell having an opening formed in a selected portion of the peripheral edges of a pair of substrates in opposing relation. After an electrolyte is charged through the opening, the primary sealing is conducted by coating an epoxy resin adhesive to the opening while an external pressure is vertically applied to the substrates followed by releasing the pressure to allow the sealant to enter into the inside of the opening and cure therein. After a certain period of time, the secondary sealing is carried out by coating an epoxy resin adhesive on the peripheral edges of the substrate including the primary sealed portion and allowing the adhesive to cure it self
This method is recognized as being applicable to the production for a electrochromic device of a relatively small size. However, the method is not always suitable for the production for an electrochromic device of a relatively large size because the primary sealing requires the process of applying an external pressure onto the cell. Furthermore, this two-step sealing method is mainly focused on the injection port (opening) provided on the end surface of the cell. Therefore, when this method is employed for producing the large electrochromic device, there may arise a risk that the adhesive would peel off due to the stress applied to the sealing portion upon transportation of the device even though the sealing is completed in a satisfactory manner.
Japanese Laid-Open Publication No. 6-250230 proposes a method by which an electrolyte injection port is sealed vaith a radiation cure type adhesive and then sealed with an epoxy resin adhesive so as to be overlapped with the former adhesive. However, with this method the above risk can not be removed because it also attempts to solve the above problem by providing the electrolyte injection port in the end surface of the cell.
An object of the invention is to provide a method for producing an electrochromic device of which sealing portion of the electrolyte injection port is free from the peel off of the adhesive by providing the electrolyte injection port in one of the two opposing substrates, not in the peripheral edge of the cell, even upon the production of a large size electrochromic device on which stress would possibly applied during the transportation of the device,
Another object of the invention is to provide a method for producing an electrochromic device. The method can avoid completely the contact between an electrolyte and an adhesive to be used for sealing the electrolyte injection port and thus is also free from a risk that the curing reaction of the adhesive is hindered.